1. Field
Embodiments described herein generally relate to composite products made with binder compositions catalyzed by one or more Lewis acids, where the binder composition includes one or more tannins and one or more multifunctional aldehydes and methods for making and using same.
2. Description of the Related Art
The production of composite wood products and composite fiber products require a binder to bond the discrete wood particulates or fibers to one another. Such conventional binders contain formaldehyde, which can be harmful to humans and the environment. Such formaldehyde based binders include urea-formaldehyde (“UF”), melamine-formaldehyde (“MF”), phenol-formaldehyde (“PF”), melamine-urea-formaldehyde (“MUF”), and phenol-urea-formaldehyde resins (“PUF”). While these formaldehyde based binders produce composite wood products and composite fiber products having desirable properties, formaldehyde is released during the production of the binder, during cure of the composite product containing the binder, as well as, from the final composite products made using the binder.
Various alternative binders have been studied in an attempt to reduce the amount of formaldehyde based binder or completely replace the formaldehyde based binder altogether in the production of composite products. One type of binder that has been studied includes the use of tannins. The tannins can be combined with formaldehyde based binders to reduce the overall concentration of formaldehyde in the binder, used alone, or mixed with a hardener or curing agent such as hexamethylene tetramine, paraformaldehyde, silica, boric acid, or the like. These attempts to reduce formaldehyde emission, however, are accompanied with one or more undesirable effects such as binders that continue to emit more formaldehyde than desired, longer cure times, reduced shelf-life of the resin, reduced product strength, reduced tolerance for processing variations, and/or inferior moisture resistance.
There is a need, therefore, for improved binder compositions for making composite products having reduced or no formaldehyde emission.